Make DD more stable

[NoureldinYosri]

Avoid error in add_dynamical_decoupling when PhasedXZGate differs
from a Clifford gate by small numerical round-off.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.60%. Comparing base (6922063) to head (52acf72).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8130   +/-   ##
=======================================
  Coverage   99.60%   99.60%           
=======================================
  Files        1118     1118           
  Lines      101003   101029   +26     
=======================================
+ Hits       100603   100629   +26     
  Misses        400      400           

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[eliottrosenberg]

LGTM. Thanks, @NoureldinYosri!

[pavoljuhas]

Let us not add an extra tol argument if not used. Also please see inline for a couple of more tweaks.

Otherwise LGTM.